Charged particle accelerators, radar, and communications systems are but a few of the many applications that require electromagnetic ("EM") energy characterized by high peak power. For example, in a particle accelerator, the voltage per unit length gained by a charged particle traversing an accelerator section varies as the square root of the peak power. Thus a high peak power results in high particle voltages for relatively short distances. This is especially desirable for medical and industrial accelerators such as those used for sterilizing hospital equipment and for food processing. Applications such as flash radiography require bursts of short pulses (100 ns pulses separated by a fraction of a microsecond).
One prior art technique for achieving high peak power is known as the chirp method of pulse compression. In the chirp method, the frequency of the EM energy is modulated monotonically, the frequency modulated pulse is propagated through a dispersive element, and the propagated pulse is subjected to frequency demodulation. The later portions of the pulse travel faster and in effect catch up with the earlier portions. The method has the disadvantage of requiring a dispersive element, and further suffers from the problem of residual frequency modulation.
U.S. Pat. No. 4,467,284 to Farkas shows a technique for converting continuous electromagnetic energy to periodic high amplitude pulses. The technique is effective, but requires continuous electromagnetic energy storage and a finite length of time to reach steady state, rendering it unsuitable for pulse inputs. Moreover, the system includes active control elements that are required to operate at high power levels, which can be a problem. Since the peak power limits of active devices are typically lower than those of passive devices, the active control elements themselves operate to place an upper limit on the peak powers that are attainable by such systems.
U.S. Pat. No. 4,009,444 to Farkas et al. discloses a passive radio frequency peak power multiplier. The device is effective, but because of reflections, the efficiency is limited to a maximum of 81%. Furthermore, that maximum efficiency can only be obtained at a compression ratio of about 3:1, and drops off sharply as the compression ratio deviates from 3:1. Moreover, the compressed pulse power varies with time, which reduces the efficiency when the compressed pulse is used as the power input to an accelerator section.